Today, vehicle drivers generally use paper maps, or in some cases electronic maps, to guide them to their destinations. Thus, drivers select their routes based on static data, generally resulting in non-optimal use of the road network under actual conditions. This is because congestion information is not known to drivers and as a result they are not able to navigate so as to avoid the congestion. Anecdotal traffic and road condition information is occasionally available from radio broadcasts, and in rare instances by variable message signs that have been installed in the infrastructure. Such information sources, however, are sparse in the information that they convey and difficult for many drivers to act upon. For example, for a driver unfamiliar with an area, information such as "congestion ahead" from a variable message sign will not provide sufficient information to allow the driver to alter his original route. Non-recurring congestion (e.g., traffic accidents) can cause immense traffic tie-ups and delays. If drivers upstream from these events had adequate information about the congestion and about alternative routes, however, the resulting congestion could be rackreduced. In addition, if a plurality of alternative routes are available and if the drivers could be guided in such a way as to optimally use the alternative routes, then the congestion resulting from an incident, as well as from normal traffic patterns, could be greatly minimized.
U.S. Pat. No. 5,172,321 teaches a method by which dynamic traffic information is communicated to vehicles over a wireless modality so that route selection algorithms in the vehicle can select an optimum route. This is an improvement, but can itself result in unstable traffic flow. Each vehicle receives the same information, and drivers have no knowledge of the route selections of other drivers, allowing the likely possibility of subsequent traffic instability (e.g., traffic jams) if many vehicles choose the same alternate route based on the same information. This system requires a high bandwidth to communicate all dynamic traffic data to all cars in areas with a dense road infrastructure. As a result, to be practical, the system must limit its information broadcast to traffic conditions of the most heavily traveled routes.
As can be seen, a need has arisen for a system for determining optimal traffic flow based upon current and projected traffic and road information, and for communicating that information to vehicles.